You should use a VPN if you are concerned about your privacy. Your ISP can see all the sites and stuff you access through their connection. They may sell your data to advertisers, and also government can also monitor you easily.
Agree, Protonmail offers free VPN which is pretty good considering it is free. The paid version is of course better but.. Protomail is also all about a safe and secure internet ( in terms of privacy). I would recommend you look into it.